Spacecraft component bearing

Abstract

A spacecraft component bearing unit for resisting axial lead due to launch vibration. This component includes a stator having drive coils, an inertia wheel having a ring magnet, a shaft having a fixed upper bearing cartridge and a floating lower bearing cartridge mounted on the stator and supporting the inertia wheel, three snubber units spaced peripherally at equal angles around an axis of the shaft, and each snubber unit having a piston with a face engaging the shaft and having a bellows connected to the piston for withdrawing the piston from contact with the shaft upon exposure to vacuum pressure at launch completion.

The embodiments of an invention in which an exclusive property or right is claimed are defined as follows: 
     
       1. A spacecraft component comprising: a stator having an elongate axis;   a first bearing cartridge supported by the stator;   a second bearing cartridge axially spaced from the first bearing cartridge and supported by the stator;   a shaft supported by the first and second bearing cartridges for shaft rotation;   an inertia wheel supported by the shaft; and   a snubber unit having a piston with a piston face for engaging the shaft and having a piston actuator,   wherein the piston actuator has an actuator housing slidably supporting the piston and has a bellows means for displacing the piston relative to the shaft in a radial direction.   
     
     
       2. The component of claim 1, wherein the bellows means has an inner bellows connected at a radially inner end to the piston support, and has an end wall connecting to a radially outer end of the inner bellows, and has a cover joined to the stator with a cover opening through which the inner bellows passes, and has an outer bellows connected at a radially inner end to the cover and connected at a radially outer end to the piston support. 
     
     
       3. The component of claim 2, wherein the shaft has a rotor having a radially outer surface engaged by the snubber piston face, and wherein the first bearing cartridge is a dual race floating cartridge and the second bearing cartridge is a dual race fixed cartridge, and wherein the fixed cartridge has a labyrinth seal disposed adjacent to the snubber unit. 
     
     
       4. The component of claim 3, wherein the cover has a valve housing having a check valve with an evacuation port for maintaining ground pressure within the housing and on the inner bellows and for maintaining piston face contact with the rotor radially outer surface until launch completion. 
     
     
       5. A spacecraft component comprising: a stator having an elongate axis;   a first bearing cartridge supported by the stator;   a second bearing cartridge axially spaced from the first bearing cartridge and supported by the stator;   a shaft supported by the first and second bearing cartridges for shaft rotation;   an inertia wheel supported by the shaft; and   a snubber unit having a piston with a piston face for engaging the shaft and having a piston actuator,   including a second snubber unit and a third snubber unit each peripherally spaced at a 120 degree spacing from the snubber unit and each being identical in structure to the snubber unit.   
     
     
       6. A method of absorbing vibration overload on a spacecraft component wheel assembly shaft during launch including the steps of: providing a fixed bearing unit mounted on a stator of the spacecraft component and journaled on a stator shaft coaxially along a common axis;   providing a snubber piston slidably mounted on the stator and in engagement with the rotor shaft;   providing a cover disposed over the fixed bearing unit and snubber piston and joined to the stator;   providing a bellows unit mounted on the cover over an opening in the cover and subject to a pressure differential between inner and outer sides of the cover;   affixing the piston at its radially outer end to the bellows unit;   whereby the decreased pressure on the outer side of the cover and bellows after launch withdraws the piston away from the stator shaft allowing rotation of the rotor shaft relative to the stator and withdrawing support by the piston of the rotor shaft.